1. Field of the Invention
The present invention relates to an optical coupler and a method of producing the same, and more particularly, it relates an optical coupler which comprises a plurality of all plastic fibers.
2. Description of the Prior Art
The Japanese Patent Laid-Open Gazette No. 62-153906 discloses an optical coupler (See FIG. 1). The optical coupler is formed by a plurality of optical fibers 1 each of which has a core 1a and a clad 1b surrounding the core 1a. More precisely, intermediate portions 2 of the optical fibers 1 are dipped in sulfuric acid to remove the clads therefrom, following which the optical fibers 1 are bundled up while the intermediate portions thereof being in contact with each other. Then, the exposed cores 1a are thermally fused together.
The prior art is employed with glass fibers in which a core 1a is made of glass material such as quartz, and therefore requires further improvement when employed with all plastic fibers in which a core 1a is made of plastic material. This is because: Cores 1a are thermally fused after bundled up in intermediate portions 2. This causes the cores 1a in intermediate portions 2 to shrink upon. Consequently, optical loss such as excess loss increases. In addition, clads 1b near the intermediate portion 2 would also be heated during fusing, causing serious problems in the all plastic fibers 1. The problems with the all plastic fibers 1 include deformation due to the molten clads 1b and deteriorated characteristics resulting from diffusing the clad material into the cores 1a. Diffusion of the clad material is particularly problematic because it largely increases optical loss.